Centrifugal force operated switch



Patented July 27, 1954 CENTRIFUGAL FORCE OPERATED SWITCH Thomas H. Darnell, Memphis, Tenn., assignor t the United States of America. as represented by the Secretary of the Navy Application September 15, 1943, Serial No. 502,521

6 Claims.

This invention relates to switches and more particularly to a centrifugally controlled switch of novel construction which is held in one position by centrifugal force acting upon a biasing member and is automatically moved to another position by the biasing member when the centrifugal force decreases to a predetermined value.

One object of the invention resides in the provision of a centrifugally controlled switch of simple and compact construction which is positive and accurate in operation.

Another object of the invention is to provide a switch of the character described which is readily adjustable to vary the centrifugal force required to maintain the switch in one position.

A further object of the invention is to provide a switch of the character described which is adapted for use in a rotary projectile and includes means for positioning the parts relative to each other and to the projectile so as to insure proper actuation of the switch under control of centrifugal force.

Still another object of the invention resides in the provision of a centrifugally controlled switch which may be readily assembled and is adapted for manufacture at low cost.

These and other objects of the invention may be better understood by reference to the accompanying drawing, in which Fig. 1 is a longitudinal sectional View of part of a projectile embodying one form of the new switch;

Figs. 2 and 3 are enlarged side and plan views, respectively, of the switch shown in Fig. 1;

Fig. 4 is a longitudinal sectional view of the switch, and

Fig. 5 is a longitudinal sectional view on the line 55 in Fig. 4.

Referring to the drawing, the numeral I0 designates an explosive projectile having a casing I I and a nose !2 threaded on the casing. A longitudinal bore I3 is formed in the nose end of the casing in offset relation to the axis of the projectile and is adapted to receive the switch I4 of the invention, part of the switch projecting into an aligned recess I5 in the nose.

The switch comprises a generally cup-shaped casing I6, which may be made of metal, fitted closely in the bore I3. Near its closed or rear end, the casing is provided in its side wall with a threaded opening I! for receiving aniadjustment screw I8. The screw extends through the interior of the casing I6 transversely thereof and has a reduced end portion or guide stem Illa which fits closely in an opening I9 diametrically opposed to the opening I1. Intermediate its ends, the adjustment screw has a shoulder 20 forming a fixed contact. Since the screw I8 is anchored at its ends in diametrically opposed openings in the casing wall, the contact shoulder 20 is held securely against displacement by forces incident to acceleration and flight of the projectile when it is fired from a gun.

The interior of the casing I6 is enlarged near its open end to form an internal shoulder 22 for supporting an insulating plug 23. The plug 23 fits closely in the casing and is retained on the shoudder 22 by the front end portion of the casing which is crimped or bent over against a bevelled surface 23a on the front end of the plug, as shown at 24.

The side wall of easing I6 at its front end is cut away over a portion of its periphery, as shown at 2B, the cut-away portion extending rearwardly for a substantial distance and terminating in a reduced slot 27 disposed intermediate the ends of the cut-away portion 26. A lug 28, which may be integral with the plug 23, projects outwardly from the side wall of the plug and through the slot 21, for a purpose to be described presently.

A contact arm 30, make of spring metal, is supported on the plug 23 in spaced relation to the side walls of the switch casing. The arm 30 extends rearwardly from the plug into the casing and is normally engaged at its free end with the contact 20. As shown, the part of arm 39, held by the plug 23 is offset laterally from the reduced portion I8a and contact 20 of the screw and toward the opening ll, so that the arm is flexed by contact 20 and normally exerts a spring action thereon. Preferably, the plug 23 is molded around the contact arm 30. The lug 28 on the plug, by engagement in the slot 21, serves to position the arm 30 so that its. rear or contact end is properly aligned with the fixed contact 20. The arm 36 projects through the front end of plug 23, as shown at 30a, and has an opening 3i near its front end for receiv ing a wire, so that the end 30a of the arm forms one terminal of the switch. A screw 32 is threaded in the front end portion of the casing I6 and forms the other terminal in the switch.

The switch casing I6 is inserted in the bore I3 in the projectile so that the lug 28 is disposed in a recess in the nose end of the projectile casing. Thus, the lug 28 serves the dual function of locating the switch arm 30 with respect to the cooperating fixed contact 20 and positioning the switch casing in the projectile so that the arm 30 is offset from the axis of rotation of the projectile (to the left of the axis as seen in Fig. 4) and is disposed with its face normal to an intersecting radius from the projectile axis.

When the projectile is fired, the centrifugal force incident to its rotation overcomes the spring action of arm 30 and moves the free end thereof away from the fixed contact 20, thereby opening the switch. As long as the projectile rotates at or in excess of a predetermined speed, the centrifugal force prevents the free end of arm 30 from engaging the fixed contact 20, thereby maintaining the switch open. However, when the speed of rotation of the projectile decreases below the predetermined speed, the free end of arm 30 is moved by the spring action of the arm into engagement with contact and closes the switch. The speed of rotation at which the spring arm may return into engagement with contact 20 is determined by adjustment of the screw 18. That is, tightening of the screw l8 moves the fixed contact 20 farther from the axis of rotation so that the switch closes at a relatively higher speed of rotation, while loosening of the screw moves the fixed contact 20 nearer to the axis of rotation so that the switch cannot close until the speed of rotation of the projectile has decreased to a relatively low value.

It will be apparent that the new switch is compact and rugged in construction and is adapted for quantity production at low cost. By reason of the plug 23 and its lug 28, the switch may be readily assembled by inserting the plug with its spring arm into the open end of the casing and adjusting the plug until the lug 28 moves into slot 21, and then locking the plug in the casing, as shown at 24. The exposed part of the plug in the cut-away portion 26 may serve as a means for preventing the wire to terminal 30a from short-circuiting against the switch casing.

The switch of my invention may be used for various purposes. For example, it may be used to close a circuit to a squib (not shown) in the projectile for automatically destroying the projectile when its speed of rotation decreases below a predetermined limit, in the event that the projectile fuze fails to operate. Also, the switch may be employed to break a short circuit in an electrically operated fuze. While the switch is illustrated in a form particularly adapted for use in rotary projectiles, it may be used in various other devices which are acted upon by centrifugal force, or the like. 1

Although the switch as illustrated is normally closed and opens at a predetermined rate of spin, it will be understood that the parts may be arranged so that the switch is normally open and closes at a predetermined rate of spin.

I claim:

1. A centrifugally controlled switch comprising a casing open at one end, a fixed contact in the casing, an insulating plug closing said end of the casing, and a spring arm on the plug extending into the casing and maintained out of engagement with the fixed contact by centrifugal force when the switch is rotated, the arm being movable into engagement with said contact when the centrifugal force decreases to a predetermined amount.

2. A centrifugally controlled switch comprising a casing having an opening, an adjustable screw in the casing forming a contact, a plug in said opening, and a spring arm on the plug extending into the casing and maintained out of engagement with said contact by centrifugal force when the switch is rotated, the arm being movable into engagement with said contact when the centrifugal force decreases to a predetermined amount depending upon the adjustment of said screw.

3. A centrifugally controlled switch comprising a fixed contact, a spring arm having a movable contact coacting. with the fixed contact and movable on the arm between open and closed positions relative to the fixed contact, the spring arm normally maintaining said movable contact in one of said positions relative to the fixed contact and being movable by centrifugal force when the switch is rotated to displace the movable contact to the other of said positions relative to the fixed contact, the spring arm being operable to return said movable contact toward said first position relative to the fixed contact when the centrifugal force decreases a predetermined amount, means for insulating said contacts from each other, and means for adjusting the relative positions of said contacts.

4. The combination with an explosive rotating projectile having a nose formed with a bore in oiiset relation to the axis of said nose, of a centrifugally controlled switch including a casing open at one end, a fixed contact in the casing, an insulating plug closing said open end of the casing, a spring arm on the plug extending into the casing and maintained out of the engagement with the fixed contact by centrifugal force when the projectile is rotated, the arm being moved into engagement with said contact when the centrifugal force decreases to a predetermined amount, and means on the insulating plug and extending radially therefrom for positioning the switch in the casing so that said spring arm is maintained offset from the axis of rotation of the projectile.

5. The combination recited in claim 4, wherein said means consists of 2. lug.

6. The combination recited in claim 4;, including a slot formed in the casing to receive said means, said means and. said slot cooperating for locking the plug against rotation in the casing.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,300,537 Williams Apr. 15, 1919 1,415,430 Dean May 9, 1922 1,441,407 Dean Jan. 9, 1923 1,776,796 Ruhlemann Sept. 30, 1930 2,103,589 Lee et al. Dec. 28, 1937 

